1. Field of the Invention
The present invention relates to an on-demand type ink jet head suitable for printing apparatuses such as a printer, a plotter, a copying machine, or a facsimile machine which is used as an image output terminals of printing system, to a method of manufacturing a thin-film coil preferable for the manufacture of the ink jet head, and to a printing apparatus.
2. Description of the Related Art
Proposed on-demand ink jet heads are based on various ink ejection methods.
One of these methods is what is called a thermal ink jet method, which uses thermal energy. With the thermal ink jet method, electricity is conducted through an electrothermal transducer or ejection heater provided inside an ink ejection opening to generate heat to cause a liquid (ink) to bubble. Thus, the pressure of the bubble causes the ink to be ejected through the ejection opening as a small droplet, which then deposit on a printing medium for printing. For example, Japanese Patent Application Laid-open No. 54-59936 (1979) or an operation manual attached to bubble jet printers xe2x80x9cBJ-10vxe2x80x9d manufactured by Canon Co., Ltd. Contains principle diagrams for this technique and describe in detail the structure of printing apparatuses based on this technique.
Ink jet heads based on another ink jet method employ a piezoelectric member such as a piezoelectric element. With this method, electricity is conducted through the piezoelectric element to deform it, so that generated pressure is provided to ink to eject it as a small droplet. A printing head based on this method is disclosed in Japanese Patent Application Laid-open No. 47-2006 (1972) (inventor: Edmond L. Keiser), and this is, so to speak, the origin of the modern ink jet heads. A recent example of an ink jet head is disclosed in Japanese Patent Application Laid-open No. 5-24189 (1993), and is mounted in ink jet printers xe2x80x9cHG5130xe2x80x9d or xe2x80x9cStylus800xe2x80x9d manufactured by Seiko Epson Co., Ltd. and other printers.
Furthermore, an ink jet head based on another ink ejection method employs an electrostatic drive method and is disclosed in Japanese Patent Application Laid-open No. 6-8449 (1994). Its operation principle is such that a potential is applied to a small space to generate Coulomb""s force to displace an electrode, so that the resulting pressure pushes out ink.
On these various methods, the thermal ink jet method employs ink mainly composed of water and containing a coloring material such as a dye and an organic solvent. A temperature of about 300xc2x0 C., is required to bubble this ink on the ejection heater in a preferable manner, whereas at a high temperature higher than 300xc2x0 C, the dye is decomposed, and the decomposed pieces may be accumulated on the surface of the ejection heater to cause so called cogation. The cogation may reduce the uniformity of the bubbling to vary the volume or ejection speed of ejected ink. Accordingly, it has been recognized as an obstacle to the improvement of image quality. Further, a cavitation impact, which occurs the moment the bubble disappears, may mechanically damage the surface of the ejection heater to affect the lifetime of the ink jet head. Consequently, a technique of further increasing the lifetime of the ink jet head has been desired.
Furthermore, with the piezoelectric element method, a large piezoelectric element must be used for generating a sufficient pressure to eject a droplet. Thus, it is difficult to densely mount a large number of ejection openings. Moreover, in a process of manufacturing an ink jet head, a machining step is required to produce piezoelectric elements mostly composed of ceramics. However, it is relatively difficult to provide precision machining so as to eject an equal amount of ink through each ejection opening. Furthermore, since the generated pressure is low, if bubbles are generated or mixed in the ink, they may absorb the pressure to make the ejection unstable.
Moreover, an ink jet head based on the electrostatic drive method is constructed more simply than one based on the piezoelectric method, but provides a very weak Coulomb""s force, thereby forcing the dimensions of an actuator section to be increased in order to allow ink droplets of a required size to be ejected. It is thus difficult to densely mount a large number of ejection openings. Further, the size of the actuator section restricts the design of ink channels, thereby hindering high-speed printing from being achieved.
Since the various ejection methods have advantages but also have problems to be solved as described above, the inventor examined whether or not any different ejection method could be employed for this purpose. During this process, the inventor designed an ink ejection method of providing a member that is displaced or deformed according to electromagnetic force, and exerting ejection pressure on the ink using the displacement or deformation of the member associated with the application of electromagnetic force and restoration of the member associated with elimination of electromagnetic force.
Then, the inventor found a conventional example of such an ink ejection method using electromagnetic force as disclosed in Japanese Patent Application Publication No. 62-9431 (1987). However, it has recently been desirable to provide high-quality prints at a printing density as high as several hundred to one thousand and several hundred dpi (dots/inch) using several picoliters of ink droplets. To accommodate such a demand, a large number of ejection openings must be densely mounted. However, although the above publication discloses the basic concept of an ink ejection method using electromagnetic force, it provides no specific suggestion for an ink jet head or a manufacture method thereof which meets the above demand.
It is a main object of the present invention to employ an ejection method using electromagnetic force, while employing a new arrangement for an actuator as an electromagnetic-force-acting portion, to solve the problems with the existing ink jet heads described in the above xe2x80x9cPrior Artxe2x80x9d section and enable high-definition images to be printed at a high speed so that the images can maintain high quality over time.
In a first aspect of the present invention, there is provided an ink jet head comprising:
an electromagnet portion having a core provided on a substrate and a thin-film coil provided on the substrate so as to surround the core and having at least one turn; and
a displacing portion located opposite the electromagnet portion, supported so as to be partially displaceable by magnetic force generated by the electromagnet portion in response to electric conduction, and for causing ink to be ejected in response to pressure resulting from the displacement.
In a second aspect of the present invention, there is provided an ink jet printing apparatus for executing printing on a printing medium using an ink jet head, the apparatus comprising:
means for relatively scanning the ink jet head and the printing medium, and
the ink jet head having:
an electromagnet portion having a core provided on a substrate and a thin-film coil provided on the substrate so as to surround the core and having at least one turn; and
a displacing portion located opposite the electromagnet portion, supported so as to be partially displaceable by magnetic force generated by the electromagnet portion in response to electric conduction, and for causing ink to be ejected in response to pressure resulting from the displacement.
In a third aspect of the present invention, there is provided a method of manufacturing an ink jet head, the method comprising the steps of:
forming the core on a substrate;
forming a thin-film coil on the substrate so as to surround the core; and
disposing a displacing portion opposite the core, the displacing portion being partially displaceable by magnetic force and for causing ink to be ejected in response to pressure resulting from the displacement.
In a fourth aspect of the present invention, there is provided an ink jet head comprising:
an electromagnet portion formed on a substrate; and
a displacing portion located opposite the electromagnet portion, supported so as to be partially displaceable by magnetic force generated by the electromagnet portion in response to electric conduction, and for causing ink to be ejected in response to pressure resulting from the displacement, and
wherein the electromagnet portion has a core provided on the substrate and a thin-film coil provided on the substrate so as to surround the core, the thin-film coil has a multilayered structure in which a plurality of coil patterns each having at least one turn in substantially the same plane are laminated via insulating layers, and a winding structure in which the coil patterns are sequentially connected through via hole contacts.
In a fifth aspect of the present invention, there is provided an ink jet printing apparatus for executing printing on a printing medium using an ink jet head, the apparatus comprising:
means for relatively scanning the ink jet head and the printing medium, and
the ink jet head having:
an electromagnet portion formed on a substrate; and
a displacing portion located opposite the electromagnet portion, supported so as to be partially displaceable by magnetic force generated by the electromagnet portion in response to electric conduction, and for causing ink to be ejected in response to pressure resulting from the displacement, and
wherein the electromagnet portion has a core provided on the substrate and a thin-film coil provided on the substrate so as to surround the core, the thin-film coil has a multilayered structure in which a plurality of coil patterns each having at least one turn in substantially the same plane are laminated via insulating layers, and a winding structure in which the coil patterns are connected sequentially through via hole contacts.
In a sixth aspect of the present invention, there is provided a method of manufacturing an ink jet head, the method comprising the steps of:
forming the core on a substrate;
forming a thin-film coil by laminating a plurality of coil patterns each having at least one turn in substantially the same plane so as to surround the core are laminated via insulating layers, while sequentially connecting the coil patterns through via hole contacts; and
disposing a displacing portion opposite the core, the displacing portion being partially displaceable by magnetic force and for causing ink to be ejected in response to pressure resulting from the displacement.
In a seventh aspect of the present invention, there is provided an thin-film coil having a multilayered structure in which a plurality of coil patterns each having at least one turn in substantially the same plane are laminated via insulating layers, and a winding structure in which the coil patterns are connected sequentially through via hole contacts;
wherein an electrode wiring for connecting the coil with one of the external wirings is provided on the substrate so as to be directly connected to the coil pattern of the lowermost layer facing the substrate, and
wherein another electrode wiring for connecting the coil pattern of an uppermost layer that is most distant from the substrate with the other of the external wirings has a multilayered structure in which a plurality of electrode layers are laminated on the substrate via insulating layers, and the electrode layers are electrically connected sequentially through the via hole contacts and connected to the other of the external wirings via the electrode layer of a lowermost layer facing the substrate.
In an eighth aspect of the present invention, there is provided an method of manufacturing a thin-film coil, the method comprising the steps of:
forming a thin-film coil main body by laminating a plurality of coil patterns each having at least one turn in substantially the same plane, while sequentially connecting the coil patterns through via hole contacts;
forming an electrode wiring for connecting the thin-film coil with one of the external wirings on the substrate so as to be directly connected to the coil pattern of a lowermost layer facing the substrate; and
forming another electrode wiring for connecting the thin-film coil main body with the other of the external wirings simultaneously with the forming step of the thin-film coil main body, by laminating a plurality of electrode layers on the substrate via insulating layers so as to connect a lowermost electrode layer facing the substrate with the other of the external wirings and to connect an uppermost electrode layer with connect the coil pattern of an uppermost layer, while sequentially connecting electrode layers through via hole contacts.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.